Single pass lead having retractable, actively attached electrode for pacing and sensing

ABSTRACT

A single-pass endocardial lead electrode adapted for implantation on or about the heart and for connection to a system for monitoring or stimulating cardiac activity including a lead body with a circumferential outer surface. The lead includes a first distal end electrode which has a first electrical conducting surface which is for positioning within the ventricle of the heart. The lead body also has a second electrode which has a second electrical conducting surface adapted for positioning within the atrium of the heart. Both of the first and the second electrodes are adapted for positioning and fixation to the wall. An active fixation element is used as part of the second electrode. The lead body also includes a curved portion which facilitates the positioning and fixing of the second electrode. 
     In another embodiment, the main lead body includes a recess into which an atrial lead body and the active fixation element attached to one end can travel from a recessed position to a position for fixation to the wall of the heart. The active fixation element which can also be moved by turning the terminal pin.

RELATED APPLICATIONS

This patent application is a division of Ser. No. 09/121,006, filed Jul.22, 1998, now U.S. Pat. No. 6,152,954, issued on Nov. 28, 2000, thespecification of which is hereby incorporated by reference. This patentapplication is also related to U.S. patent application Ser. No.09/121,018, entitled “SINGLE PASS DEFIBRILLATION/PACING LEAD WITHPASSIVELY ATTACHED ELECTRODE FOR PACING AND SENSING” which is assignedto a common assignee and is filed on a date even herewith. The relatedapplication is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of leads for correctingarrhythmias of the heart. More particularly, this invention relates to alead having an electrode for more effective delivery of electricalcharges to the heart.

BACKGROUND OF THE INVENTION

Electrodes implanted in the body for electrical cardioversion or pacingof the heart are well known. More specifically, electrodes implanted inor about the heart have been used to reverse (i.e., defibrillate orcardiovert) certain life threatening arrhythmias, or to stimulatecontraction (pacing) of the heart, where electrical energy is applied tothe heart via the electrodes to return the heart to normal rhythm.Electrodes have also been used to sense and deliver pacing pulses to theatrium and ventricle. The electrode in the atrium senses the electricalsignals that trigger the heartbeat. The electrode detects abnormallyslow (bradycardia) or abnormally fast (tachycardia) heartbeats. Inresponse to the sensed bradycardia or tachycardia condition, a pulsegenerator produces pulses or signals to correct the condition. The samenode used to sense the condition is also used in the process ofdelivering a corrective pulse or signal from the pulse generator of thepacemaker.

There are four main types of pulses which are delivered by a pulsegenerator. Two of the signals or pulses are for pacing the heart. Firstof all, there is a pulse for pacing the heart when it is beating tooslowly. The pulses trigger the heart beat. The pulses are delivered at arate to increase the heart rate to a desired level. The second type ofpacing, called antitachycardia pacing, is used on a heart that isbeating too fast. In antitachycardia pacing, the pacing pulses aredelivered initially at a rate faster than the beating heart. The rate ofthe pulses is then slowed until the heart rate is at a desired level.The third and fourth type of pulses are used when the heart is beatingtoo fast and the heart is fibrillating. The third type is calledcardioversion. This is delivery of a relatively low energy shock,typically in the range of 0.75 to 1 joule, to the heart. The fourth typeof pulse or signal is a defibrillation signal which is the delivery of ahigh energy shock, typically up to 34 joules, to the heart.

Sick sinus syndrome and symptomatic AV block constitute the majorreasons for insertion of cardiac pacemakers today. Cardiac pacing may beperformed by the transvenous method or by electrodes implanted directlyonto the epicardium. Transvenous pacing may be temporary or permanent.In temporary transvenous pacing, an electrode lead is introduced into aperipheral vein and fluoroscopically positioned against the endocardium.The external terminals of the leads are connected to an external cardiacpacemaker which has an adjustable rate and milliamperage control.Temporary transvenous pacing is utilized (1) prior to the insertion of apermanent pacing system and (2) in situations in which the indicationfor pacing is judged to be reversible (drug-induced AV block orbradycardia) or possibly irreversible and progressive (AV and bundlebranch blocks associated with myocardial infarction).

Permanent transvenous pacing is implanted under sterile surgicalconditions. An electrode lead is generally positioned in the rightventricle and/or in the right atrium through a subclavian vein, and theproximal electrode terminals are attached to a pacemaker which isimplanted subcutaneously.

Some patients require a pacing system to correct an abnormally slowheart (bradycardia condition) as well as a defibrillation system todetect when the heart starts beating abnormally fast (tachycardiacondition) and to defibrillate or deliver a pulse to the heart tocorrect the abnormally fast heartbeat. In the past, a common practicefor a patient having both of these conditions would be to provide twodifferent leads attached to the heart. One would be implanted fordelivering pacing signals to the heart to correct for the bradycardiacondition. A separate lead would be implanted to sense a fast beatingheart and defibrillate the heart to correct for the tachycardiacondition. One lead is placed in the atrium and the other lead is placedin the ventricle.

Having two separate leads implanted within the heart is undesirable formany reasons. Among the many reasons are that the implantation procedurefor a implanting two leads is more complex and also takes a longer timewhen compared to the complexity and time needed to implant a singlelead. In addition, two leads may interact with one another afterimplantation or in vivo which can result in dislodgment of one or bothof the leads. In vivo interaction may also cause abrasion of theinsulative layer along the lead which can result in an electricalfailure of one or both of the leads. Another problem is that as moreleads are implanted in the heart, the ability to add other leads isreduced. If the patient's condition changes over time the ability to addleads is restricted. Two separate leads also increase the risk ofinfection and may result in additional health care costs associated withimplantation and follow-up.

Because of these problems, a single lead having electrodes for bothpacing and sensing in both chambers of the heart has been used. Theseleads are called single pass lead designs. Current single pass leaddesigns have problems. One of the more significant problems is thatcurrent single pass lead designs utilize “floating” electrodes orelectrodes which are not attached to the endocardial wall of the heart.The floating electrodes lay in the blood pool or against the endocardialwall of the heart and the electrode may move slightly within the heart.The electrode positioned within the atrium of a single-pass endocardiallead generally is an electrically conductive cylindrical ring orsemicylindrical ring structure, which does not allow for tissue ingrowthinto the electrode. Since the location of the electrodes is not fixedwith respect to the atrial wall, the electrical performance of theseelectrodes varies and is generally less than optimal. Both theelectrical sensing capability as well as the pacing delivery capabilityof such electrodes are suboptimal. The pacing parameters of such afloating electrode are also suboptimal.

Some atrial leads have passive fixation elements that affix to theatrium over time. A problem with these leads is that the electrodes aremuch more likely to be displaced from the wall of the atrium than thosethat have an active fixation element. When the electrodes are placed farfrom the wall, there can be some fairly substantial effects. Forexample, the electrode may be unable to sense a tachycardia condition.Another example might be that signals for pacing may be ineffective.Additional power may have to be used to pace the heart thereby depletingenergy from the battery of the pulse generator of the pacing system.

There is a real need for a single-pass endocardial pacing lead that hasan electrode for active fixation to the wall of the atrium of the heart.A single-pass lead equipped with such an electrode would allow forbetter sensing capability and better pacing delivery to the heart. Inaddition, there is a need for a single-pass lead having an electrode forpositioning within the atrium that allows for tissue ingrowth. Tissueingrowth further enhances the electrical performance of the electrode.In addition, the lead and electrode is further stabilized within theheart as a result of tissue ingrowth. There is also a need for asingle-pass endocardial lead which has an electrode for placing withinthe right atrium of the heart that accommodates elutinganti-inflammatory drugs.

SUMMARY OF THE INVENTION

A single-pass endocardial lead electrode adapted for implantation in theheart and for connection to a system for monitoring or stimulatingcardiac activity includes a lead body with a circumferential outersurface. The lead includes a first distal end electrode or pair ofelectrodes for positioning in the ventricle and a second proximalelectrode or pair of electrodes for positioning in the atrium. Thesecond electrode or pair of electrodes are adapted for positioning andfixation to the wall of the atrium of the heart. An active fixationelement is used as part of the second electrode or electrode pair. Thelead body also may include a curved portion which facilitates thepositioning and fixing of the second electrode or second pair ofelectrodes. The lead body also includes at least one recess forpositioning an active fixation element within the recess.

In another embodiment, the recess is able to house the active fixationelectrode as well as a portion of a lead body associated with the atrium(atrial lead body). By moving the terminal pin with respect to a yoke,the lead body is moved out of the recess. The atrial lead body can be astraight lead or a J-shaped lead. The type of atrial lead body used willdepend on the placement of the lead within the atrium of the heart andthe preference of the surgeon doing the placement. The advantage is thatthe active fixation electrode is placed into the recess during placementof the lead to prevent it from attaching inadvertently to the subclavianvein or other tissue while it is being inserted.

One of the embodiments includes the use of an active fixation electrodethat can be controllably moved from a recessed position to an attachmentposition by rotating the terminal pin attached to the conductor coilwhich is attached to the body of the active fixation electrode.

Advantageously, the electrodes are attached to the endocardium so thatthe electrical signals received from the heart are better than withfloating, unattached electrodes. In addition, the active fixationelectrodes can be placed into a recess so that mechanisms, such as ahelical hook, used to attach the electrode to the wall of the heart willnot catch undesired tissue. A further advantage is that only one leadneeds to be placed into the patient to do both sensing and pacing of alltypes. The lead can also be shaped to facilitate placement of the lead.

The extendable portion of the lead is mechanically isolated from themain lead body so that the helical screw or hook can turn independentlyof the lead body. In other words, the body of the lead does not need tobe turned to affix the helical screw to the heart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the single-pass endocardial lead forelectrically stimulating the heart.

FIG. 2 is a cross section view of the atrial electrode of thesingle-pass endocardial lead showing the active attachment element in aretracted position.

FIG. 3 is a cross section view of the atrial electrode portion of thelead showing the active attachment element for active attachment to theatrial wall of the heart in an extended position.

FIG. 4 is a side view of another embodiment of a lead for activefixation attachment to the atrial wall of the heart.

FIG. 5 is a side view of the embodiment of the lead shown in FIG. 4 withthe atrial lead body in an extended position for active attachment tothe atrial wall of the heart.

FIG. 6 is a side view of the embodiment of the lead shown in FIG. 4 withthe atrial lead body in an extended position for active attachment tothe atrial wall of the heart.

FIG. 7 is a perspective view of another embodiment of a lead for activefixation to the wall of the heart.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

Curved Lead with Atrial Active Fixation Element

This invention is directed toward an active fixation element used inseveral types of leads. One type of lead will be described first to notonly describe one embodiment of the invention but to also set forthgenerally the environment of the invention. After describing the firstlead embodiment, the active fixation element will be detailed. Next, theother embodiments of the lead will be described.

FIG. 1 is a side view of one type of lead 100 for delivering electricalpulses to stimulate the heart. The lead 100 is comprised of a connectorterminal 110 and a lead body 120. The lead 100 attaches to a pulsesensor and generator 140. The lead body has a number of electrodes inthe distal end 130 which is implanted within the heart. The connectorterminal 110 electrically connects the various electrodes and conductorswithin the lead body to a pulse sensor and generator 140. The pulsesensor and generator 140 contains electronics to sense various pulses ofthe heart and also produce pulsing signals for delivery to the heart.The pulse sensor and generator 140 also contains electronics andsoftware necessary to detect certain types of arrhythmias and to correctfor them. Physicians are able to program the pulse sensor and generatorto correct a particular arrhythmia that the patient may have. It shouldbe noted that there are numerous types of connector terminals whichconnect to a pulse sensing and generating unit 140. The lead terminalconnector 110 provides for the electrical connection between theelectrodes on the lead 100 and pulse generator 140. The connectorterminal end 110 shown is designed to international IS-1Standard ISO5841-3(E).

The lead body 120 is cylindrical in shape. The lead body 120 is a tubingmaterial formed from a polymer biocompatible for implantation, andpreferably the tubing is made from a silicone rubber polymer. Thesilicone rubber polymer tubing contains several electrical conductors.The electrical conductors are made of a highly conductive, highlycorrosion-resistant material which is formed into a helix. Severalseparate electrical conductors are housed within the lead body 120. Whenthere is more than one such electrical conductor within the lead body120, the lead is called a multifilar lead. The electrical conductorscarry current and signals between the pulse sensor and generator 140 andthe electrodes located at the distal end 130 of the lead 100.

After the lead 100 has been implanted, the distal end 130 of the leadbody 120 is situated within the heart. The distal end 130 of the leadbody 120 includes a curved or bias portion 150 and a straight portion160.

After implantation, the curved or biased portion 150 will generally belocated in the right ventricle of the heart. The straight portion 160 ofthis lead body will generally be located in the right atrium. The distalend 130 of the lead 100 has four electrodes. The first electrode 154 isprovided at the farthest distal end of the lead for the purpose ofdelivering ventricular pacing therapy. The first electrode 154 isgenerally called the distal electrode. A second electrode 153 is locatednear the first or distal electrode 154 and can be used as a counterelectrode for electrode 154 or as a current source for defibrillationtherapy. This electrode 153 is sometimes referred to as a ventricularshocking coil. A third electrode 161 is located at a more proximalposition for the purpose of delivering atrial pacing therapy. Thiselectrode 161 is intended to be actively attached to the atrial wall ofthe heart. The third electrode 161 is also referred to as the proximalelectrode. A fourth electrode 162 is located near the electrode 161 andcan be used as a counter electrode for electrode 161 or as part of adefibrillation therapy system. The fourth electrode 162 is sometimescalled the SVC shocking coil. The lead 100 may be generally described asa tachycardia or tachy lead. The shocking coils 153 and 162 areelectrically conductive rings made of an alloy of platinum and iridiumwhich is highly conductive and highly resistant to corrosion. Theelectrode 161 uses the active fixation element described below. Theelectrode 154 may include an active fixation or passive fixationportion. It should be noted that the lead shown and described above is abipolar lead in that the positive and negative portions of a circuit arelocated in the lead body 100. It should be noted that this lead may alsobe made a unipolar lead. In other words, one electrode of the lead body100 can be the shocking coil and the other electrode can be the signalgenerator.

The shape of the curved portion 150 of the lead is important. Therelaxed shape of the lead body 120 conforms to the shape the lead isexpected to take after implantation. The distal portion of the straightportion 160 and the proximal portion of the curved portion 150 arebiased to conform to the mid-portion of the atrial wall. This shapefacilitates the placement of electrode 161 against the atrial wallduring implantation. Furthermore, because the natural unstressed shapeof the lead before implantation is approximately the same afterimplantation, this reduces the nominal residual stresses in the leadbody. Also, this will reduce the nominal forces between the atrial walland the point of attachment of the electrode 161 in the atrium. Theshape of the middle and end portions of portion 150 conforms to theshape of the upper ventricular chamber below the tricuspid valve andventricular septal wall. This shape will tend to cause the lead 100 tolie across the top of the ventricle in a gradual arc with the electrode153 lying against the ventricular septum and electrode 154 resting inthe ventricular apex. This lead position is advantageous because the arcshape will tend to reduce the transmitted forces between the leadfixation points at electrode 161 in the atrium and electrode 154 in theventricle as they move relative to each other during heart rhythm. Thispreformed shape will ease the surgeon's task of positioning of lead 100and, particularly, of the electrode end 130 such that less time isrequired and the placement procedure is less prone to error.

As mentioned previously, electrode 161 is designed to be attached to thewall of the atrium of the heart. FIG. 2 shows electrode 161 in arecessed position. FIG. 3 shows electrode 161 actively attached to thewall of the atrium. In this embodiment, the electrode 161 includes anactive fixation screw 163 which is a helical screw. The atrial electrode161 is configured to initially rest inside the lead body 120, and thenextend and rotate independent of the lead body 120 for atrialattachment. FIG. 2 shows the electrode 161 and the fixation screw 163resting within the lead body. A seal 170 is shown in FIGS. 2 and 3. Theseal 170 prevents body fluids from traveling into the recess in the leadbody. The seal 170 is made of a biocompatible material such as siliconerubber. The seal 170 may take any appropriate shape. In this instance,the seal 170 is shaped as a permanent O-ring affixed to the recess inthe lead body. This covered position of the electrode 161 and activefixation screw 163 makes the lead placement process easier since theatrial electrode 161 does not snag the vein during initial venous accessand subsequent movement of the lead to the heart. The seal 170 can alsobe used to hold a lubricant 300 within the recess of the body of thelead. The lubricant 300 will allow the atrial electrode 161 to move frominside the recess to outside the recess with greater ease. The lubricantcan be a substance such as fluorosilicone which is biocompatible.

FIG. 3 shows the electrode 161 extended from the lead body. Theelectrode 161 and active fixation screw 163 move independent of the leadbody. This relative movement allows the electrode to come in contactwith the atrial wall without manipulation of the lead body 120. Theelectrode 161 can then be fixed by rotating the atrial electrode 161 andattached fixation screw 163. The fixation screw 163 of the atrialelectrode 161 can be advanced and retracted independent of rotation ofthe lead body. The active fixation screw and attached electrode arecontrolled from the terminal end. This is shown by turning briefly toFIGS. 4 and 5. In FIGS. 4 and 5, there is a lead housed within a recess450 in the lead body 410. The lead housed within the recess 450 can bemoved in and out of the recess 450 by moving a terminal end 442longitudinally with respect to the lead body 410. As shown in FIG. 4,the lead is within a recess when the terminal end 442 is positioned evenwith the other terminal ends. When the terminal end is moved toward thedistal end of the lead, the lead within the recess 450 is moved out ofthe recess 450. As shown in FIG. 3, this additional degree of freedomallows for movement of the lead body relative to the fixed atrialelectrode 161 without unscrewing (or over-screwing) the electrode fromthe endocardial tissue.

Returning to FIG. 3, as mentioned previously, the electricallyconductive portion 164 which either senses electrical energy produced bythe heart or delivers pacing signals to the heart is a small radiuselectrode. The electrode 161 has a diameter in the range of 0.024 inchesto 0.050 inches. The advantage of this small radius is ease of venousaccess and small surface area resulting in high impedance for savingenergy. Saving energy makes the battery used to power the pulsegenerator 140 last longer.

Also shown in FIGS. 2 and 3 is a multifilar coil 165 and an electricallyconductive sleeve 166. The conductive sleeve 166 has the smaller radiuselectrode tip 164 attached at one end of the sleeve. At the other end ofthe sleeve 166, the multifilar coil 165 is attached. The multifilar coilincludes at least one conductor which is used to carry electricalsignals to and from the electrode tip 164.

It is contemplated that slight variations in the design could be usedfor a particular application as required. One such variation would bethe provision of steroid elution from any of the electrodes 153, 154,161 and 162. Steroid elution can be provided by using one or more of thesteroid-releasing technologies such as sleeves or collars positioned inclose proximity to the electrodes or by the use of internalizedsteroid-containing plugs. Steroids are generally used in order to reducethe inflammation associated with attaching an electrode to theendocardial wall of the heart. By reducing the inflammation at the timeof implantation, the threshold values associated with the electrodes areusually lower when compared to threshold values associated withelectrodes that did not elute a steroid over the attachment site. Anexample of the composition of at least one collar is dexamethasoneacetate in a simple silicone medical adhesive rubber binder or asteroid-releasing plug similarly fabricated.

Of course, for the active fixation embodiment of this invention shown inFIGS. 1-3, various advancing and locking mechanisms can be used tomanipulate the atrial electrode 161 from the proximal end of the leadduring implantation.

Various shapes of stylets can be placed within the lead to advance andposition the lead within the endocardial wall of the heart. Oncepositioned correctly, an active fixation element is used to secure theelectrode to the wall of the heart. A locking mechanism can be employedto keep the fixation element from moving from its attached position onthe heart.

Quad Lumen With Yoke and Active Fixation

FIGS. 4, 5, and 6 show several other closely related preferredembodiments of the invention. FIG. 4 is a side view of a lead 400 whichincludes an active fixation element for attachment to the atrial wall ofthe heart. The lead 400 includes a main lead body 410, an atrial leadbody (also shown in FIGS. 5 and 6) and a ventricle lead body 420. Themain lead body 410 is attached to a yoke 430. The yoke 430 acts as astrain reliever and also has a series of terminal pins 440, 442 and 444attached to the yoke/strain reliever 430. The terminal pins 440, 442 and444 are attached to the pulse generator (not shown). The main lead body410 is longer than as shown; a break has been put into the main leadbody 410 to illustrate that the main lead body 410 is longer than thatshown in FIG. 4. The main lead body 410 includes a recess 450. Theatrial lead body (shown in FIGS. 5 and 6) fits within the recess 450 inthe main lead body 410. When the atrial lead body is housed within therecess 450, an active fixation element on the end of the atrial leadbody and associated with the proximate electrode is also housed withinthe recess. Advantageously, the active fixation element will not hook orsnag tissue when it is housed within the recess 450. Typically, theatrial lead body is pulled back or housed within the recess 450 when thelead 400 is being surgically implanted into the patient. Typically, thelead 400 is placed in the subclavian vein of the patient and then passedthrough the subclavian vein to the inner chambers of the heart. Once thelead and, more specifically, the distal electrode and the proximalelectrode are within the ventricle and atrium of the heart, the variousleads are removed from their respective recesses so that a surgeon canattach them to the inner wall of the heart.

FIG. 5 is a side view of the embodiment of a lead 400 shown in FIG. 4.FIG. 5 has a J-shaped atrial lead body 500 which emerges from the recess450 in the main body of the lead 410. On the end of the atrial lead 500is an active fixation element 510. The active fixation element 510typically includes a helically shaped hook for screwing into the atriumof the heart. The J-shape of the lead facilitates positioning of the endof the electrode having the active fixation element 510 to a desiredposition within the atrium. The J-shape eases positioning within theatrium of the heart when certain portions of the atrium are the targetfor connection of the active fixation element 510. Once properlypositioned, a surgeon can turn the active fixation element 510 causingit to hook the tissue in the inner wall of the heart. The atrial lead500 is moved with respect to the recess by pushing the terminal pin from442 forward with respect to the yoke 430. A conductor connects theterminal pin 442 and the active fixation element 510. By moving theterminal pin 442 inward with respect to the yoke 430, the conductormoves with respect to the main body 410 of the lead 400′. This causesthe atrial lead body 500 to emerge or pass through or pass out of therecess 450 in the main body 410. The terminal pin 442 and the activefixation element attached to it move independently of the lead body 400.Twisting the terminal pin causes the active fixation element 510 on theatrial lead 500 to turn and affix itself to the atrial wall of theheart. A locking mechanism may be provided to prevent the activefixation element 510 from “backing out” after it has been affixed to thewall. The atrial lead 500 is prestressed so that it will take theJ-shape upon leaving or coming out of the recess 450.

FIG. 6 is a side view of another embodiment of the lead shown in FIG. 4.In this particular embodiment, the lead 400″ has a straight atrial lead600 which comes out of the recess 450 in the main lead body 410. Theposition of the atrial lead 600 is controlled by movement of theterminal pin 442 with respect to the yoke 430. Moving the terminal pinwith respect to the yoke 430 causes the atrial lead 600 to come out ofthe recess 450. An active fixation element 510 is positioned on the endof the atrial lead 600. Once the surgeon positions the atrial lead 600and the active fixation element 510 at the end of the atrial lead in aproper position or desired position, the active fixation element 510 isused to attach the proximal electrode to the endocardial wall of theatrium.

FIG. 7 shows another embodiment of the invention wherein the atrial leadportion 600 does not have the ability to move in and out of a recess.Rather, the atrial lead 600 is permanently extended with respect to thelead body 410. The active fixation element 510 on the atrial lead 600 iscovered with a dissolvable coating 710, such as mannitol. Thedissolvable coating 710 remains intact during insertion of the lead 400″through the subclavian vein and into the heart. The dissolvable coating710 prevents the active fixation element 510 from catching tissue in thevein during insertion. The coating dissolves to expose active fixationelement 510 and allow it to be turned into the atrial wall of the heart.In FIG. 7, the dissolvable coating 710 is depicted by a dotted lineenclosure around the active fixation element 510. Both leads have anexposed active fixation element and both are actually covered with thedissolvable coating. The terminal pin 442 is turned to rotate the activefixation element 510. The active fixation element 510 can be turned orrotated independently of the lead body 410.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A method comprising: coupling a connector with alead body; forming a continuous curved portion in the lead body, thecurved-portion including at least one curve, the continuous curvedportion extending from a first end to a second end which conforms to ashape of an upper ventricular chamber below a tricuspid valve andventricular septal wall; coupling first and second electrodes directlyadjacent to first and second ends of the continuous curved portion,respectively; coupling a third electrode along the curved portion of thelead body; disposing the lead body within a heart and placing the thirdelectrode against the ventricular septum and resting the secondelectrode in a ventricular apex.
 2. The method as recited in claim 1,further comprising forming the curved portion in the lead body prior toinsertion of the lead body into a heart and prior to insertion ofinstruments therethrough.
 3. The method as recited in claim 1, furthercomprising disposing the first end of the curved portion in an atrium ofthe heart, and disposing the second end of the curved portion in aventricle of the heart.
 4. The method as recited in claim 1, whereincoupling the third electrode along the curved portion comprises couplinga defibrillation electrode along the curved portion, and furthercomprising disposing the defibrillation electrode in a ventricle of theheart.
 5. The method as recited in claim 1, further comprising advancingan active fixation member with a terminal pin.
 6. The method as recitedin claim 1, further comprising coupling a fourth electrode along astraight portion of the lead body, and the fourth electrode is adefibrillation electrode.
 7. The method as recited in claim 1, furthercomprising locking an active fixation mechanism to the active fixationelement from backing out from a heart wall.
 8. A lead assemblycomprising: a lead body extending from a proximal end to a distal endand having an intermediate portion therebetween, the lead body having apreformed continuous curved portion extending from a first end to asecond end, wherein the preformed continuous curved portion isconfigured to allow the first end to be placed in a ventricle of a heartand the second end to be placed in an atrium of the heart; at least onepreformed straight portion disposed directly adjacent to the preformedcurved portion, and the straight portion configured to be positionedwithin the atrium and the preformed continuous curved portion configuredto be substantially positioned within the ventricle; at least onedefibrillation electrode associated with the preformed continuous curvedportion of the lead body; and the defibrillation electrode extends fromthe distal end of the lead body along the preformed continuous curvedportion.
 9. The lead as recited in claim 8, further comprising a firstelectrode disposed at the first end of the preformed curved portion. 10.The lead as recited in claim 8, further comprising a second electrodedisposed between the preformed straight portion and the preformed curvedportion.
 11. The lead as recited in claim 8, wherein further comprisingan electrode disposed within a lumen of the straight portion of the leadbody.
 12. The lead as recited in claim 8, further comprising a firstelectrode disposed at the first end or the second end of the preformedcurved portion, and a second electrode disposed between the preformedstraight portion and the preformed curved portion.